(ECG, EKG, Resting ECG, Resting EKG)
An electrocardiogram (ECG or EKG) is one of the simplest and fastest procedures used to evaluate the heart. Electrodes (small, plastic patches) are placed at certain locations on the chest, arms, and legs. When the electrodes are connected to an ECG machine by lead wires, the electrical activity of the heart is measured, interpreted, and printed out for the doctor's information and further interpretation.
Other related procedures that may be used to assess the heart include exercise electrocardiogram (ECG), Holter monitor, signal-averaged ECG, cardiac catheterization, chest X-ray, computed tomography (CT scan) of the chest, echocardiography, electrophysiological studies, magnetic resonance imaging (MRI) of the heart, myocardial perfusion scans, radionuclide angiography, and cardiac CT scan. Please see these procedures for additional information.
The heart is, in the simplest terms, a pump made up of muscle tissue. The heart's pumping action is regulated by an electrical conduction system that coordinates the contraction of the various chambers of the heart.
An electrical stimulus is generated by the sinus node (also called the sinoatrial node, or SA node), which is a small mass of specialized tissue located in the right atrium (right upper chamber) of the heart.
The sinus node generates an electrical stimulus regularly at 60 to 100 times per minute under normal conditions. This electrical stimulus travels down through the conduction pathways (similar to the way electricity flows through power lines from the power plant to your house) and causes the heart's lower chambers to contract and pump out blood. The right and left atria (the two upper chambers of the heart) are stimulated first and contract a short period of time before the right and left ventricles (the two lower chambers of the heart).
The electrical impulse travels from the sinus node to the atrioventricular node (also called AV node), where impulses are slowed down for a very short period, then continue down the conduction pathway via the bundle of His into the ventricles. The bundle of His divides into right and left pathways to provide electrical stimulation to the right and left ventricles.
This electrical activity of the heart is measured by an electrocardiogram. By placing electrodes at specific locations on the body (chest, arms, and legs), a graphic representation, or tracing, of the electrical activity can be obtained. Changes in an ECG from the normal tracing may indicate one or more of several heart-related conditions.
Almost everyone knows what a basic ECG tracing looks like. But what does it mean?
The first short upward notch of the ECG tracing is called the "P wave." The P wave indicates that the atria (the two upper chambers of the heart) are contracting to pump out blood.
The next part of the tracing is a short downward section connected to a tall upward section. This next part is called the "QRS complex." This part indicates that the ventricles (the two lower chambers of the heart) are contracting to pump out blood.
The next short upward segment is called the "ST segment." The ST segment indicates the amount of time from the end of the contraction of the ventricles to the beginning of the rest period before the ventricles begin to contract for the next beat.
The next upward curve is called the "T wave." The T wave indicates the resting period of the ventricles.
When the doctor views an ECG, he or she studies the size and length of each part of the ECG. Variations in size and length of the different parts of the tracing may be significant. The tracing for each lead of a 12-lead ECG will look different, but will have the same basic components as described above. Each lead of the 12-lead ECG is "looking" at a specific part of the heart, so variations in a lead may indicate a problem with the part of the heart associated with a particular lead.
Some reasons for your doctor to request an ECG include, but are not limited to, the following:
There may be other reasons for your doctor to recommend an ECG.
An ECG is a quick, noninvasive method of assessing the heart's function. Risks associated with ECG are minimal and rare.
Prolonged application of the adhesive electrode patches may cause tissue breakdown or skin irritation at the application site.
There may be other risks depending on your specific medical condition. Be sure to discuss any concerns with your doctor prior to the procedure.
Certain factors or conditions may interfere with or affect the results of the test. These include, but are not limited to, the following:
An ECG may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your doctor's practices.
Generally, an ECG follows this process:
You should be able to resume your normal diet and activities, unless your doctor instructs you differently.
Generally, there is no special care following an ECG.
Notify your doctor if you develop any signs or symptoms you had prior to the test (for example, chest pain, shortness of breath, dizziness, or fainting).
Your doctor may give you additional or alternate instructions after the procedure, depending on your particular situation.
The content provided here is for informational purposes only, and was not designed to diagnose or treat a health problem or disease, or replace the professional medical advice you receive from your doctor. Please consult your health care provider with any questions or concerns you may have regarding your condition.
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